feat(ai-service): stateless extraction service with grounding verifier

[Fluory]

Goal

services/ai exposes POST /v1/extract (contract contracts/ai-service.openapi.yaml): docling parses PDF and EML into segments with locators, Gemini on Vertex eu extracts three header fields, and a deterministic verifier checks every quote.

Acceptance criteria

• OpenAPI 3.1 contract committed; TS client/types generated from it
• Segments carry stable locators (PDF: page + bounding box, EML: body line)
• Per field: value | null, status found/uncertain/missing, evidence {segmentId, quote} for company, contact person, requested delivery date
• Verifier (test-first): quote not found (normalised) in the cited segment, or value inconsistent with the quote → unverified
• No database or storage credentials; bearer-token auth; logs without document content
• Model and region from configuration; the Gemini free tier only with an explicit dev flag and never as a silent fallback (fail-closed)
• PR documents the verified docling EML/MSG coverage and the SDK configuration for the eu endpoint (ADR-0001 open points)

Not part of this task

• All fields and positions, XLSX/DOCX/MSG/scans, eval gate (Epic 2)

Affected areas

• services/ai/
• contracts/ai-service.openapi.yaml

Test plan

Criterion	Check
grounding verifier	pytest unit tests incl. normalisation of numbers and dates
contract	contract test against the OpenAPI schema
end to end	pytest with a recorded model response at the HTTP boundary (synthetic mail)

Security/Privacy affected?

Yes – document content reaches an external LLM: EU endpoint, synthetic data only, no content in logs. Prompt-injection case in the tests.

Epic: #2 · Architecture: docs/decisions/ADR-0001-pilot-architecture.md

[Fluory]

Claimed by @Fluory (Claude Code cloud session, overnight run) on branch claude/feat-ai-service-6 – stacked on claude/feat-intake-upload-5 (#32). The Python service was built in parallel by a subagent in an isolated worktree (test-first commits preserved); draft PR follows.

---

Generated by Claude Code